JPH0766913B2 - Grinding blade management circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> This invention is intended for precision grinding, in processes such as semiconductor manufacturing.
The present invention relates to an electric circuit for managing the state of the cutting edge of a grinding blade that rotates at high speed in a dicing device that performs processing such as grooving and for managing the replacement time of the grinding blade.

<Prior Art> For example, a dicing machine is used as a wafer grooving device during semiconductor manufacturing. With a dicing machine, precision groove cutting is performed with a round blade (grinding blade) that rotates at a high speed of 10,000 rpm or more, but almost unattended, but grinding occurs when the blade edge is broken or the blade has reached the end of its life. If you continue
An irregularity of the grinding line becomes severe, an accident such as cracking occurs, and the yield of semiconductors is reduced.
Therefore, various automatic blade management has been considered. For example, the shape of the groove that is the result of grinding is measured (Japanese Patent Laid-Open No. 54-
No. 109681), which is to be judged by the vibration of the machine base during grinding (Japanese Patent Laid-Open No. 54-113583). In addition to this, the blade is irradiated with light, and the reflected light is received by a detector to determine the output signal (Japanese Patent Laid-Open Nos. 54-109682, 60-62444 and 59-122209). No.)

If you want to judge based on the groove shape, it is not possible to perform measurement unless you finish the grinding work or stop the machine in the middle and wipe the surface of the grinding blade cleanly. It's not right.
In addition, the method using vibration during driving has a drawback that it is difficult to determine the relationship between vibration and blade loss because the grinding blade rotates at a very high speed. Incidentally, it is disclosed in the above publication that the light is applied to the blade and the reflected light or the passing light is detected by the detector to detect the state of the blade, but how the detection signal is processed to determine the state of the blade. Nothing is shown to judge. That is, the grinding fluid is constantly jetted to the grinding blade during high-speed rotation and grinding, and the chips adhere to and separate from the grinding blade, and the detection signal is unstable.Therefore, it is necessary to generate a signal for judging the state of the blade. However, this is not shown at all. Therefore, the technique of the above publication cannot be put to practical use as it is.

The present invention eliminates the need for a light source with good linearity by irradiating light in a narrow range from a close distance by sandwiching a grinding blade that rotates at a high speed by an optical fiber, reducing the influence of grinding water, and The response speed can be increased by detecting the change in light intensity, and the effect of grinding water can be removed by adding a time measurement circuit to the change in light intensity, and at the same time, the size of the grinding edge can be reduced. With a grinding blade management circuit that can know the degree, and a circuit that determines the life of the blade by comparing the output signal with the setting reference signal, by comparing the grinding blade status signal to a signal that is averaged through a low-pass filter. It controls the replacement time of the grinding blade.

<Means for Solving Problems> In the present invention, the photodetector output of the photodetector consisting of the projector and the photoreceiver provided via the optical fiber in close proximity to each other with the grinding blade rotating at a high speed interposed therebetween is branched, One signal is passed through a low-pass filter and averaged, the other signal is amplified, and a sudden change in the signal is detected by the first comparator circuit that makes the difference between the two signals, and the signal is clock pulsed to the grinding blade. Two judgments are made to judge the size of the defect of the grinding wheel, and to make the status signal of the grinding blade an averaged signal through a low-pass filter, and compare it with the set reference signal to judge the life of the blade with the output signal. The signal controls the grinding blade.

<Examples> Examples of the present invention will be described below with reference to the drawings.

FIG. 1 shows the constitution of the present invention. The constitution of the present invention will be described with reference to FIG.

Light is projected toward the tip of the rotating thin disc grinding blade 1.
The tips of the optical fibers 2 and 3 for light reception are fixed, and the projector 4 and the light receiver 5 are attached to the other ends.

Then, the light receiver 5 converts the amount of light into a voltage and outputs the voltage, which is passed through a preamplifier and branched into two.

The waveform of the signal a output from the amplifier is shown in FIG.

In FIG. 2, the vertical axis of the waveform indicates a state in which a large amount of reflected light is present (upper level), and the lower portion (low level) represents a state in which less reflected light is present.

In a, a small vertical movement has partial unevenness of reflection due to roughening of the surface of the blade, and the recessed portion is caused by a portion of the blade where the reflected light is small due to the lack of the blade. The horizontal axis shows the time greatly extended.

The reflected light signal obtained by the light receiver 5 passes through the preamplifier 6 and is divided into two, one passes through the preamplifier 7 and enters the first comparator 9, and the other signal passes through the low-pass filter 8 and is averaged. Then, the first comparator 9 detects a sudden change in the reflected signal. That is, the signal c obtained by averaging the reflection signals output from the low-pass filter 8 (the response to the sudden change in the signal is slow because it passes through the integrating circuit) becomes the reference signal of the first comparator, and the grinding blade is in a normal state with no defects. The offset of the preamplifier 7 is adjusted by so that the signal b is slightly higher than the signal c. By performing this adjustment, the signal of the first comparator is not inverted with respect to the gentle DC fluctuations (clouding of the light-projecting surface and light-receiving surface due to grinding fluid or the like, and light quantity change due to wear of the grinding blade). (The low level continues.) Also, a sudden change signal due to the loss (loss) of the grinding wave passes through the amplifier 7 and becomes the compared signal of the first comparator, and is compared with the output signal of the low-pass filter 8 described above to output from the first comparator output. It is output as a grinding blade loss signal d. This defect signal d is input to the defect determination circuit 10 and the time length (pulse width) of the signal is used to determine the size of the defect (defect) of the grinding blade by the clock pulse, and this is used as a defect warning signal. That is, a clock pulse e (cycle t) is input from the outside to the loss determination circuit 10 to cause m, n protruding in the waveform d.
The number of clock pulse periods t included in each pulse is counted. Now, as shown in the waveform f, the protrusions m and n of the waveform of d are such that m is t × 1 and n is t × 3. Suppose you have.

Here, since the circumference of the measuring point of the grinding blade, the number of revolutions of the blade, and t are known, the dimension corresponding to t can be known. This makes it possible to read the lengths of m and n. Therefore, if the cutting portion of the blade in one rotation of the grinding blade is separated with t, and is tabulated, the broken state of the blade can be found.

Further, for example, if a warning of t × 3 or more is required, this can be output as a warning display signal. That is, it is possible to generate a signal for managing the lack of the grinding blade.

FIG. 3 shows a model of the wear condition of the grinding blade due to long-term use with the amount of reflected light taken along the vertical axis. The right side of the figure shows that the amount of protrusion of the grinding blade 1 in FIG. 1 decreases. Therefore, the reflected light amount gradually decreases. At this time, the output signal averaged through the low pass filter 8 in FIG.
In the waveform c ′ in the figure, it gradually descends as shown by the solid line. Then, in the second comparator circuit 11, the solid line waveform of the waveform c'in FIG. 2 contacts the reference voltage p contacted by the dotted line.

At this time, the life of the blade is set and the warning signal g is output. That is, the defect management signal and the life warning signal are used to manage the life judgment as well as the defect of the grinding blade.

<Effect> As described above, according to the present invention, the defective portion of the grinding blade can be detected by the length.

Therefore, by using the signal of one revolution of the grinding blade, it is possible to know how many defects (chips) have occurred on the entire circumference of the grinding blade, and the length of the grinding blade (chips). By setting the replacement condition of the grinding blade by, a warning can be displayed immediately when the setting condition is met.

Further, at this time, the fluctuation of the signal (DC fluctuation) due to the environmental change that occurs during a long time during the grinding process is canceled by the comparison of the signals b and c, so that there is no influence, and the defect of the grinding blade detects the sudden change of the signal. It can be accurately detected in real time. Characterized by this.

Further, by adding a small number of circuits to the above circuit, it is possible to comprehensively control the replacement time of the grinding blades together with the life of the grinding blades.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG.
Output waveform explanatory diagram at each point in the figure, Fig. 3 shows the relationship between the life of the grinding blade and the reflection amount Figure 1: Rotary blade (grinding blade), 2: Optical fiber 3: Optical fiber, 4: Emitter 5: Receiver, 6: Preamplifier 7: Amplifier 8: Low-pass filter 9: First comparator 10: Missing judgment circuit 11: Second comparator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-60-177847 (JP, A) JP-A-61-252051 (JP, A) JP-A-62-94209 (JP, A) JP-A-60- 62444 (JP, A) JP 55-90248 (JP, A) JP 57-204414 (JP, A) Actually opened 53-156984 (JP, U) Actually opened 60-139280 (JP, U)

Claims (1)

[Claims] 1. A photodetector of a photodetector comprising a light emitter and a light receiver, which are provided in close proximity to each other via an optical fiber in a dicing device for grinding while ejecting a grinding liquid onto a workpiece, with a grinding blade rotating at a high speed interposed therebetween. The output is branched, one signal is passed through a low-pass filter to be an averaged signal,
A first comparator circuit that amplifies the other signal and creates a difference between the two signals detects a sudden change in the photodetector output signal of the photodetector, and determines the size of the grinding blade defect with that signal and a clock pulse. Circuit, through the roper filter, averaged signal, and the output signal of the second comparator circuit that compares the reference signal that can be set arbitrarily, the circuit that determines the life of the grinding blade of the grinding blade Grinding blade management circuit that manages replacement time.